You know the accelerator functionality added to Internet Explorer 8. There is an Accelerator Platform for Windows 7 with a whitepaper on the Platform, and documentation on all the interfaces and methods.
This means you can add accelerator functionality into Word, Excel, Windows Live Writer or any other application. How about a built in translator for AutoCAD or Revit? This would be a cool thing to spice them up with when using Windows 7. Adding search functionality, look up a definition, terminology and so on.